“Families first”: A messaging slogan that politicians – often but not exclusively Democrats – use to appeal to couples with children, who are more likely to vote than unmarried people.

“Let’s put families first, and make sure our policies match how you actually work and live in the 21st century,” Hillary Clinton said last week in propounding one of her campaign’s main themes. “Families look a lot different today than they did 30 years ago, and so do our jobs.”

Beyond identifying with the concerns of people with kids, “families first” is enduringly popular because it lets voters fill in the blanks for themselves on what should come second – corporations, the wealthy, or some other less-deserving demographic.

It’s a co-option of “family values,” which conservatives started using in the 1980s to defend the interests of traditional families. “Families First” also was the title of a 1992 report from a commission that GOP President George H.W. Bush’s administration appointed to study urban households.

That year, Bill Clinton won the presidency on a theme of “putting people first.” But the party “sharpened it” to its current form when Mr. Clinton sought reelection, wrote Virginia Tech communications professor Robert E. Denton Jr. in his book “The 1996 Presidential Campaign: A Communication Perspective.” (Mrs. Clinton’s use of it thus helps tie her – subtly – to her husband.)

Almost exactly 20 years ago, the Democratic leaders in the House and Senate at the time, Missouri’s Richard Gephardt and South Dakota’s Tom Daschle, rolled out the “Families First” platform – more tax deductions for educational expenses; expanded child-care tax credits; a law to help job-changers to transfer their pensions; cutting inheritance taxes for family-owned businesses and a loss of tax benefits for companies shifting jobs overseas. House Republicans dismissed it as “tiny ideas from tiny minds.”

It has persisted ever since, becoming more prevalent lately. In the current session of Congress, it has surfaced 39 times in bills or House and Senate floor debates, according to the Congressional Record. If that trend continues, it would represent the most frequent usage since the 2007-08 session.

Despite its association with Democrats, Republicans sometimes invoke it. In Minnesota, GOP lawmakers two years ago unveiled a “Families First” plan that included reducing sales taxes and repealing business-to-business taxes. More recently, House and Senate lawmakers crafted a bipartisan bill – which the House passed this month – to enable states to redirect child foster-care money to services such as parent training. Its title: “The Family First Prevention Services Act.”

The bill “does exactly what the title suggests — it puts families first,” said House Ways and Means Committee Chairman Kevin Brady (R) of Texas. The bill focuses on addressing problems in the home by delivering parents much-needed support, rather than sending a child straight into foster care.”